Load cell with nesting bearing rings



1961 A. H. EL WAZIRI 3,005,337

LOAD CELL WITH NESTING BEARING RINGS Filed Sept. 14, 1960 Af/amey UnitedStates Patent 3,005,337 LOAD CELL WITH NESTING BEARING RINGS Abdel H. ElWaziri, Pittsburgh, Pa., assignor to United States Steel Corporation, acorporation of New Jersey Filed Sept. 14, 1960, Ser. No. 56,000 4Claims. (Cl. 73-141) This invention relates to an improved load cellwhich is simple and compact and has a wide range of capacity.

Load cells of known design are usually bulky and complex in constructionand are limited to the measurement of loads in a relatively narrowrange.

In its preferred form, my improved cell comprises a base plate having acollapsible pancake chamber thereon filled with a liquid which is butslightly compressible. A plurality of nesting concentric bearing membersare disposed on the chamber and the latter is connected to a pressuregage. The pressure developed in the liquid by the application of a loadmeasures the magnitude thereof. The number of said members used forsupporting any given load governs the area ofapplication and thus therange of the cell. The number of members acting in support of a load maybe altered by changing intermediate range-selector plates of dilferentsizes.

A complete understanding of the invention may be obtained from thefollowing detailed description and explanation which refer to theaccompanying drawings illustrating the present preferred embodiment. Inthe drawrngs:

FIGURE 1 is a plan view of my improved cell with the intermediate plateomitted; and

FIGURE 2 is a transverse section taken on the plane of line IIII ofFIGURE 1.

Referring now in detail to the drawings, the cell there shown comprisesa circular base plate 11 having a peripheral ring wall 12 securedthereon. A collapsible pancake chamber 13 of rubber or the like fitssnugly within wall 12 and communicates with a fitting 14 extendingradially through it. A pipe connection 15 extends from fitting '14 to agage 16.

Circular concentric nesting bearing members, including a central disc 17and rings 18 therearound, rest on chamber 13. The disc and each ringhave peripheral lower flanges 19 and the rings all have internal upperflanges 20. The disc and rings fit loosely together so that each is freeto move except as confined by the flanges of the others. The outermostring 18 is restricted from upward motion by means of an internal flange21 which is an integral part of wall 12. Plate 11 is fastened to wall 12by means of a number of set screws. Thus the Wall 12 restricts themotion of ring 18 away from plate 11, the outermost ring 18 confines thenext inner ring, and so on.

Disc 17 may be pressed against chamber 13 by an imposed load withoutany' force being applied through any of the surrounding rings exceptthat incident to their own weight. Similarly a load may be appliedthrough the disc and any desired number of rings (less than all) withoutaifecting those lying outwardly of the outermost ring under load. Inthis way the area of chamber 13 under load may be widely varied.

ice

Range-selector plates 22 of various sizes may be provided for applyingloads to various areas of chamber 13. These plates are preferablyslightly less in diameter than the plate '17 and rings 18. The plate 22shown in the drawings as supporting the load (indicated by an arrow) onthe cell, covers disc 17 and the two rings 18 adjacent thereto. Thetotal area of the disc 17 and the two adjacent rings is the only area ofchamber 13 to which external force is applied. This determines the unitpressure for a given load and the reading of gage 16.

Plate 22 may thus be considered as means for calibrating the gage to adesired range. The smaller the area of chamber 13 under external force,the smaller the load required to produce a given unit pressure in theenclosed liquid. It will be evident that, in the example given, the twooutermost rings 18, while they do not exert any pressure on chamber 13,serve to restrain expansion thereof so that the force applied by theload is sustained by an increase in the pressure of the liquid. For thesame reason, pipe 15 should be relatively inexpansible under thepressures involved, e.g., it should be of high-strength steel.

For load measurement, a first trial should be made with thelargest-diameter intermediate plate to ascertain the order of magnitudeof the load. Thereafter the size of plate may be chosen which will givethe highest reading and greatest sensitivity for the load undermeasurement. If the pressure obtained is insutficient (less thansubstantially full-scale deflection of gage 16), smaller plates may besubstituted until a suitable pressure is obtained. This procedure isreversed if the pressure obtained is too great. Pressure-loadcalibration curves may, of course, be supplied with each cell for thevarious loading discs.

It will be evident that my improved cell is characterized by a very widerange of capacity, and that any desired range may be easily selected.The cell is also compact and extremely simple in structure so as torequire little maintenance and have a long useful life.

Although I have disclosed herein the preferred embodiment of myinvention, I intend to cover as well any change or modification thereinwhich may be made without departing from the spirit and scope of theinvention.

I claim:

1. A load cell comprising a base plate, a collapsible pancake chamberlaid flatwise on said plate adapted to contain a charge of liquid, aplurality of circular concentric nesting bearing members resting on saidchamber and means for indicating the pressure developed in said liquidby a load applied to certain of said members.

2. The combination defined in claim 1, characterized by said membersincluding a central plate and a plurality of rings nestable thereon.

3. The combination defined in claim 2, characterized by said plate andrings having periphery flanges whereby each ring is supported on themember within it.

4. The combination defined in claim 1, characterized by a ringsurrounding the outermost member and confining it to said plate.

No references cited.

